In cases where multiple fallback templates are requested to the template loader (i.e.
django.template.loader.select_template()) to find the first one available, the cached template loader does not cache non-existent templates, making cached loader "slow" again if every time it has to try looking for a template that's been already found to be missing.
from django.template.loader import render_to_string
render_to_string(['missing_template_1.html', 'missing_template_2.html', ..., 'missing_template_N.html', 'existent_template.html'])
django.template.loaders.cached.Loader, and given that snippet above, and the fact that
missing_template_N.html do not exist, the filesystem loader or other loaders get hit every time (trying and trying to find already known as missing templates).
I'm attaching a patch to fix this.